Metal post-processing pipeline implementation

- Add custom Metal render target creation
- Implement post-processing without GPU-CPU-GPU copies
- Create Metal texture extraction system
- Add Metal CRT shader pipeline integration
- Modify screen rendering to use Metal when available
- Enable shaders by default for testing

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

source/screen.cpp

@@ -44,8 +44,21 @@ Screen::Screen()
     initSDLVideo();
 
     // Crea la textura de destino
+#ifdef __APPLE__
+    const auto render_name = SDL_GetRendererName(renderer_);
+    if (render_name && !strncmp(render_name, "metal", 5)) {
+        // Usar nuestra propia Metal texture como render target
+        game_canvas_ = shader::metal::createMetalRenderTarget(renderer_, param.game.width, param.game.height);
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION, "Using custom Metal render target for game_canvas_");
+    } else {
+        // Fallback para otros renderers
+        game_canvas_ = SDL_CreateTexture(renderer_, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, param.game.width, param.game.height);
+        SDL_SetTextureScaleMode(game_canvas_, SDL_SCALEMODE_NEAREST);
+    }
+#else
     game_canvas_ = SDL_CreateTexture(renderer_, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, param.game.width, param.game.height);
     SDL_SetTextureScaleMode(game_canvas_, SDL_SCALEMODE_NEAREST);
+#endif
 
     // Crea el objeto de texto
     createText();
@@ -99,7 +112,18 @@ void Screen::renderPresent() {
     clean();
 
     if (Options::video.shaders) {
+#ifdef __APPLE__
+        const auto render_name = SDL_GetRendererName(renderer_);
+        if (render_name && !strncmp(render_name, "metal", 5)) {
+            // Use Metal post-processing with our custom render target
+            shader::metal::renderWithPostProcessing(renderer_, game_canvas_);
+        } else {
+            // Fallback to standard shader system for non-Metal renderers
+            shader::render();
+        }
+#else
         shader::render();
+#endif
     } else {
         SDL_RenderTexture(renderer_, game_canvas_, nullptr, nullptr);
         SDL_RenderPresent(renderer_);